(a) Field of the Invention
The present invention relates to a synchronization and link access method in a low energy critical infrastructure monitoring network.
(b) Description of the Related Art
A low energy critical infrastructure monitoring (MECIM) network is a network for connection of sensor devices in wire areas including on the ground, under the ground, in water, or in buildings. Since the sensor devices are installed in places where repair and maintenance cannot be easily performed, the sensor devices should be operated with independent power for more than several years, and the sensor devices are required to periodically transmit data in a changeable wireless environment.
FIG. 1 shows a coordinator and an endpoint device of an LECIM network.
Referring to FIG. 1, a single coordinator is connected with a plurality of endpoint devices. FIG. 1 exemplarily illustrates four endpoint devices, but typically, one coordinator may be connected with 1000 or more endpoint devices.
Each endpoint device may generate sensing data of several tens to several hundreds of bites, and single data may be generated in one day or single data may be generated every score of seconds. Since the coordinator has no energy limit because it uses permanent energy, a transmission range and a number of transmissions have no restriction. However, each endpoint device (e.g., a battery) using independent power has a restriction in transmission range and a number of transmissions. Therefore, the endpoint device should assure reliability in transmission data while minimizing energy consumption and should successfully receive a network configuration control message from the coordinator.
However, the endpoint device consumes energy for waiting for reception of wireless signals and transmission of wireless signals, and therefore a transmission success rate of a signal that requires data transmission should be high for minimizing energy consumption and a transmission/reception process for additional frames should be minimized.
In this case, the transmission success rate is changed depending on a competition between the endpoint devices for occupying a link to the coordinator, frequency interference of other wireless devices, and the like. Therefore, a method for efficiently controlling a contention node and link occupation with a hidden node in a wireless transmission area is required for the endpoint device.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.